PURPOSE: To easily obtain a touch response which matches an actual musical performance by a player without performing any special operation by the player. CONSTITUTION: When a conversion table selection mode is entered with a velocity switch ON (step S2), velocity data obtained by keying operation similar to the actual musical performance are stored (steps S3 and S4) and when the conversion table selection mode is reset with a stop key ON (step S5), the maximum value (MAX) and minimum value (MIN) of the inputted velocity data are detected (step S6). A conversion table is selected (steps S7, S8, and S11) by comparing the detected MAX and detected MIN with previously set MAX and MIN, and the conversion table No.N is set. Then when the actual musical performance is carried out, the velocity data are converted into musical tone control data by the selected conversion table and a sounding process is performed (steps S14-S18).